Custom Post Type Advanced Slug

This is pretty straightforward using a rewrite endpoint.

The first step is to set an ep_mask when you register your taxonomy, which is part of the rewrite argument. Note that it’s a constant, and should be as-is, without quotes:

$args = array(
    'rewrite' => array(
        'slug' => 'location',
        'with_front' => false,
        'ep_mask' => EP_TAGS
    ),
    // your other args...
);

Now you can add a rewrite endpoint immediately after registering your taxonomy, also hooked to init:

add_rewrite_endpoint( 'overview', EP_TAGS );

Don’t forget to flush rewrite rules after adding or changing anything in this code. You can do this quickly by visiting the Settings > Permalinks page.

Now you’ll be able to visit

domain.com/location/england/

as well as

domain.com/location/england/overview/

To load a different template for these requests, we can use the taxonomy_template filter:

function wpd_location_overview_template( $template ){
    if( false !== get_query_var( 'overview', false ) ){
        $template = locate_template( 'location-overview.php' );
    }
    return $template;
}
add_filter( 'taxonomy_template', 'wpd_location_overview_template' );

This will load location-overview.php from your child or parent theme whenever overview is in the URL.

Use get_queried_object_id() or get_queried_object() in the template to fetch your fields associated to this term. The main query will also still contain the posts for this term, if you have any use for them.